Yarn wrapped with surface fibers locked in place by core elements



Jan. 30, 1968 F. c. FIELD. JR 3,365,872

YARN WRAPPED WITH SURFACE FIBERS LOCKED IN PLACE BY CORE ELEMENTS Filed Sept. 17. 1964 FREDERICK c. FIELD, JR

ATTORNEY United States Patent 0 "ice 3,365,872 YARN WRAPPED WITH SURFACE FIBERS LOCKED IN PLACE BY CORE ELEMENTS Frederick C. Field, Jr., Wilmington, Del., assignor to E. I. do iont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed Se t. 17, 1964, Ser. No. 397,139

Claims. (Cl. 57-144) This invention relates to improvediwrapped yarns.

An object of this invention is to provide novel wrapped yarns having improved properties over those obtainable heretofore. More specifically, it is an object to improve the surface stability, slippage resistance and knot-holding ability of wrapped yarns, particularly for the manufacture of twine. A further object is to provide a satisfactory process for preparing said novel improved yarns. A still further object is to provide suitable apparatus for preparing said yarns. Other objects will be apparent from a description of the invention given below.

The novel wrapped yarn of this invention is an improvernent over yarn prepared in accordance with my US. Patent No. 3,079,746 of Mar. 5, 1963. The yarns are similar in having surface wrappings of discontinuous textile fibers tightly twisted about a core of relatively straight textile fibers, the core fibers being held together as a compact bundle by the wrappings. There is a predominance of true twist in the wrappings and the core may be substantially free from true twist. However, the yarn of the present invention is further characterized by having a core of at least two continuous, integral core elements, such as multifilament textile yarns composed of continuous or discontinuous fibers, and by having portions of surface fibers locked in place in the core, particularly between the core elements, in a manner which holds the surface wrappings in position. The individual core elements may be twisted or free from twist, but thereis substantially no twist of the core elements about each other unless twist is introdu :ed in subsequent processing of the yarn product. Preferably the improved yarn is also characterized by the surface fibers being helically twisted tightly about the bundle of core filaments such that the twist level of said surface fibers is relatively constant along the length of the yarn.

The invention also provides a novel twist transference,

.fluid twisting process for producing the yarn which is an improvement over the process described and claimed in 'my US. Patent No. 3,079,746 of Mar. 5, 1963. This improved process involves bringing together, at a convergence point upstream from a false-twisting device, discontinuous fibers and two or more separate, continuous, integral core elements, and twisting fibers about the core elements to form the novel yarn. A further aspect of this invention is the provision of a suitable apparatus for making the above-mentioned improved yarn which comprises, in combination, a false-twisting means, means providing a convergence point upstream from said falsetwisting means, means for feeding separate core elements to said convergence point, separate means for pneumatically feeding discontinuous textile fibers to said convergence point, and means for drafting s'aid discontinuous fibers prior to contact with said core elements.

The invention will be more fully understood by reference to the accompanying drawing in which:

FIGURE 1 is a schematic representation of a specific embodiment of the process and apparatus for producing the novel yarn of this invention;

FIGURE 2 illustrates a wrapped yarn product of this invention on an enlarged scale; and

FIGURE 3 is a greatly enlarged cross-sectional view of a wrapped yarn product of this invention, illustrating that discontinuous fibers are locked in place between the core filaments, the ends of which are shown as circles, and are also wrapped around the bundle of care filaments.

In FIGURE 1, a large number of fibers or sliver 10, from a suitable source, are fed in side-by-side relationship between back rolls 12 and 14 of a conventional spinning frame, pass between a pair of control rolls 16 and 18, and between guide rolls 20 and 22 to the front drafting rolls 24 and 2.6 of the frame. Passing about the control and guide rolls are a pair of aprons Z8 and 30, which support and assist in drafting the slivers. The relative speeds of the above sets of rolls are controlled in conventional manner for normal drafting of slivers, which is usually in the range from about 20x to 100x.

The front rolls 24, 26 feed the drafted slivers as a sheet of discontinuous fibers to the novel treatment of this invention. The fibers pass directly into the back end of a hollow box-like member 32 and are borne forward in a current of air. The air current is created by suction through duct 34, which opens into the box-like member near the forward end. It may be desirable to place a screen over the duct opening to prevent removal of short fibers, but this is not necessary with usual staple lengths. Also, although a screen is sometimes useful to separate short fibers from the exiting air stream, very short fibers tend to catch in the screen and not be picked up in the yarn being produced.

Continuous core elements 36 are fed separately into 6 the box-like member through opposed openings 38 located intermediate the back and front ends of the box. Two core elements are shown entering the box through a pair of openings, but a larger number may be used to provide modified products. Also, the front rolls 24, 26 are shown controlling the feed rate of the core elements, but separate feed rolls can be used to deliver these elements at a higher or lower speed than the front rolls would provide. The continuous core elements and the airborne fibers are combined into a single strand 40 which exits from the box through an Opening 42 in the front end. The box-like member is open at the back end to receive the fibers from the front rolls and is otherwise completely enclosed except forthe additional openings mentioned above. The flattened box shown has been found highly effective for the purpose of this invention, but other shapes can obviously be used to cause the fibers to be transported in a suitable airborne condition for combination with the con tinuous core elements.

The strand 40 of combined core elements and fibers, exiting from opening 42 of the box, passes througha false twisting device 44 to Windup roll 46 which is surface driven by roll 48 to maintain the strand under uniform tension. Device 44 is preferably a torque jet but may be any of the known false twisters for introducing twist which backs up along the strand, as it travels toward the device, to a point within the box 32 Where the continuous core elements converge and are twisted together. The airborne fibers are randomly caught up by the twisting core elements and receive a lesser twist. Hence the strand passing to the false twister has a high degree of twist of the core elements about each other, and varying lesser amounts of twist of the fibers about the core. The core twist is substantially all removed as the strand travels on beyond the false twister to the take-up rolls. Because of the above non-uniform twist, the less highly-twisted surface fibers first untwist and then twist in reverse direc tion as untwisting of the core elements takes place. This phenomenon will be referred to as twist transference. The result is that the product has fibers: twisted tightly; about substanially straight core elements as illustrated in FIG- URE 2.

The yarn illustrated on an enlarged scale in FlGURE 2 has staple fibers 50 helically twisted about core elements composed of substantially straight continuous filaments Patented Jan. 30, 1968 52. The major proportion of the fibers are wrapped tightly about the core in helical bands which resemble stripes on a barbers pole. There are also a number of projecting fiber loops 54 and loose fiber ends 56. In other embodiments which have a larger proportion of fibers relative to the core elements, there may be a substantially continuous surface wrapping of fibers on the yarn core.

FIGURE 3 shows the appearance of a greatly enlarged cross-section of the above yarn. In addition to the major proportion of staple fibers 50, wrapped around the core bundle of continuous filaments 52, a minor proportion of staple fiber ends 58 are seen between filaments 52 in the core. This embodiment is made with a pair of core elements, and fiber ends 58 lie between the juncture of the two elements. Fibers having portions locked in place in the core, in this manner, are present in surface wrappings and hold the wrappings in place. In this embodiment, fibers having flattened cross sections are used so that the ends 50 and 58 are readily distinguishable from the filaments 52 of circular cross section.

Suitable raw materials for making the yarns of this invention include all synthetic and natural fibers and filaments, and combinations thereof. The filaments or fibers of the continuous core elements and the discontinuous fibers having free ends which form the wrapping elements may have the same or different cross sections and may be composed of the same or different compositions selected from the various fiber compositions exemplified below. Natural fibers that may be used include cotton, wool, silk, ramie, fiax, jute, hemp and the like. Suitable synthetic fibers include polyamides such as poly(epsilon caproamide) and poly(hexamethylene adipamide), poly (undecanoamide) and poly(heptanoamide); cellulose esters, e.g., cellulose acetate; polyesters; particularly polyesters of terephthalic acid or isophthalic acid and a lower glycol, e.g., poly(ethylene terephthalate); poly(hexahydro-p-xylylene terephthalate); polyalkylenes, e.g., polyethylene, linear polypropylene, etc.; polyvinyls and polyacrylics, e.g., polyacrylonitrile, as well as copolymers of acrylonitrile and other copolymerizable monomers (e.g., methyl methacrylate or vinyl acetate). Copolymers of ethylene terephthalate containing less then combined monomers other than ethylene terephthalate and copolyrrierizable with ethylene terephthalate are also useful in practicing this invention. Also useful in the practice of this invention are spandex fibers and yarns, multicomponent fibers such as described in Taylor US. Patent No. 3,038,237 and Breen U.S. Patent No. 3,038,236, as well as poly(meta-phenylene isophthalamide), and poly benzimidazole. Other compositions which are suitable for the two types of feed materials include metal fibers, glass fibers. and asbestos fibers.

The separate core elements for use in this invention are continuous bundles, with or without twist, composed of continuous filaments, spun yarns, monofil, mixtures of continuous filament and staple, core-spun yarns, and the like. The two or more core elements may be of the same composition and construction or they may be of different composition and/or different construction. The discontinuous fibers which are used in making the yarn must have free ends, but may be of conventional staple length or longer. For example, the discontinuous fibers may have a length varying from one inch up to twenty inches, or even higher. They may be of the same length or of a mix ture of lengths, such as is produced from a Turbo-Stapler (Turbo Machine Company, Lansdale, Pa).

The percentage of discontinuous fibers used in making the final yarn product will depend on the type of product desired and the characteristics desired in the yarn. In spinning yarns of multi-component core elements, some improvement in yarn properties can be noted when using as little as 2% to 3% of discontinuous fibers, based on the weight of final yarn product, but greater amounts are usually desirable and the products can contain 40% to of discontinuous fibers. Normally the amount of discontinuous fibers employed in making the wrapped yarns will be kept to a minor proportion of the total product by weight. The denier of the discontinuous fibers as well as the denier of the core elements are not critical, and will normally depend on the characteristics desired in 'ahe final yarn product. Suitable deniers may range from about 1 d.p.f. up to about 30 d.p.f. or even higher for operating by fluid means. Suitable false-twisting devices include torque jets of the type shown in FIGURE 4 of my US Patent No. 3,079,746 and fiuid jets of the types illustrated in the drawings of Breen et al. US. Patent No. 3,009,309 of Nov. 21, 1961.

Although it is not intended to be limited by any particular theory, it is believed that, in most of the wrapped yarn products made in accordance with this invention, the discontinuous fibers appearing as wrapping elements in the surface of the yarn are in the form of a substantially continuous wrapping element running the length of the yarn. Another observation has been noted in connection with wrapped yarns of heavy denier or multiply, wherein the surface of the wrapped yarn exhibits a barber pole" efiect when the amount of discontinuous fibers in the wrapping is relatively small. As the amoun of wrapping fibers is increased to larger amounts, this visual effect disappears and the discontinuous wrapping fibers completely cover the core elements throughout the length of the yarn.

In feeding the continuous core elements, on the one hand, and the discontinuous fibers on the other hand, so that these two feed materials meet at the stated convergence point, the relative speeds of the two feed materials may be the same or may be different. For example, the core elements may be fed to the convergence point either faster or slower than the discontinuous fiber feed. The convergence point of discontinuous fibers and core elements is normally set at a distance downstream of the nip of the feed rolls greater than the maximum length of discontinuous fibers, and preferably at a distance about twice the average fiber length, the 2% of longest fibers in mixture of different lengths, such as a Turbo product, being neglected in said average.

An important advantage of the present invention is that it provides a new wrapped yarn structure having superior surface stability, slippage resistance, knot-holding ability, and strength over wrapped yarns made heretofore. Most of the superior properties exhibited by the novel wrapped yarns are due to the discontinuous fibers which are locked in place between the core elements in the interior of the new wrapped yarns. This is a structural feature not present, for example, in the yarns described in my US. Patent No. 3,079,746. The yarns of the present invention have a distinctly different yarn structure which provides yarn characteristics and properties superior to those of the previous yarns which have no discontinuous fibers separating the core elements in the middle of the yarn. Thus yarns may be prepared in accordance with my invention to have the feel, hand and bulk of spun yarn, while also having the strength, elongation, shrinkage and modulus of a continuous filament industrial yarn.

The following examples illustrate specific embodiments of this invention, but are not intended to limit the invention defined in the appended claims.

'5 EXAMPLES A series of 16 different wrapped yarns was prepared using the equipment shown in FIGURE 1. Different fiber compositions were used; the nylon being polyhexamethylans filament yarns or comparative core-spun wrapped yarns made according to my U.S. Patent No. 3,079,746,

ene adipamide, the acrylic being an acrylonitrile polymer 5 pounqsto'break is listed for a number of Y P and the polyester an ethylene terephthalate polymer. Two vets m the table The t strength o the apw l or more continuous multifilament core elements, were fed Y of Examples 2, 2 and 16 18 much 9 w between the front rolls of the drafting frame at the inthat of a commercial cotton machine tying twine.

TABLE.

Continuous Core Elements Discontinuous Fibers Product No. of Denier Feed Percent Feed Windup Yarn n Bundles of each Fiber Speed, Total D.p.f. Fiber. Speed, Speed, Size Strength,

Bundle y.p.m. y.p.m y.p.rn. (cc lbs.

2 340 Nylon. 205 9.1 2.0 205 201 2. s5

2 s40 -do. 154 15.5 3.0 154 150 2.50

2 1,100 Polyester. 111 10.0 3.0 114 112 21s 12 840 Nylon..." 85 22.5 4.5 s5 s4 39 2 840 ..do 110 12.5 4.5 15 114 a dicated speeds in yards per minute. In Example 16, a set of core element feed rolls (not shown) were pro vided directly above the illustrated front rolls to deliver the core elements to the convergence box at a higher speed than the staple. The denier of each core'bundle of essentially zero twist multifilament yarn (except Example 8 which is a spun yarn) is listed in the table together with the feeding speeds in yards per minute and the filament composition of the core bundle. The discontinuous fibers are composed of'thc indicated fiber composition and denier per fiber, and these staple fibers are fed in the form of a sliver to the back rolls of the frame and drafted from 20X to 100X during passage to the front rolls. The staple fibers are picked up from the front rolls by a vacuum line and brought into contact with the core elements on route to the convergence point, which, in turn, is set at a distance of approximately two times the average fiber length measured downstream from the nip of the front or feed rolls. The staple fibers forming the sliver in all except Examples 12 and 13 were obtained from continuous filaments which had been broken on a Turbo-Stapler machine, resulting in a distribution of fiber lengths with an average fiber length of approximately 3 inches. The nylon staple was combed top, having an average fiber length of about 3 inches. The table indicates the weight percent of staple fiber which was used in making each yarn, based on the combined weights of the continuous elements and of the discontinuous elements in the final wrapped yarn product. The feeding speed of the sliver at the feed rolls is also given in the table. The false twisting device used in making the 16 yarn samples was a fluid jet of the type shown in FIG- URE 4 of my US. Patent No. 3,079,746, which was operated with compressed air at about 95 p.s.i.g. at room temperature. The wrapped yarns were guided to a surface driven windup (speed shown in the table). The yarn size is listed in terms of cotton count.

The yarn products were highly useful as industrial twines, especially for the machine tying of mail. The yarns of Examples 2, 9, 12, 14 and 16 were also useful for making upholstery fabrics. The yarn products listed in the table all had good surface stability and good knotholding ability. The knot retention of the yarn products was far superior to either conventionally plied continu- The present invention provides a wide variety of different yarn structures made from different fiber compositions as described and exemplified above. The wrapped yarns are useful for preparing a number of different types of woven, knitted, non-woven, and tufted fabrics, both in the industrial textile field as well as the apparel textile field. Products which maybe made include sewing. thread; yarns for use in industrial fabrics, coated fabrics, industrial hose reinforcement, fire hose, industrial belts, conveyor belts, V-belts and webbing; yarns for special cordage applications, such as' water wicking, upholstery, carpets and tire cord; industrial and household cords and twines, including twine for machine tying of magazines, mail and the like, baler twine and hand twine; and specialty wrapped yarns for use as an effect thread in styling different types of fabrics, and the like.

Since many different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

I claim:

1. A wrapped yarn comprising a core composed of at least two continuous integral core elements of textile fibers and surface wrappings composed of discontinuous textile fibers, the surface fibers being tightly twisted about the core with portions of fibers locked into place in the core, and the core fibers being relatively straight and held together as a compact bundle by the surface wrappings.

2. A wrapped yarn as defined in claim 1 wherein said surface wrappings are staple fibers helically twisted about the core at a relatively constant twist level along the yarn.

3. A wrapped yarn as defined in claim 1 wherein said core elements are bundles of continuous filaments and are substantially free from twist.

4. A wrapped yarn as defined in claim 1 wherein said core elements are spun yarns composed of discontinuous fibers and there is substantially no twist of the core elements about each other.

5. A wrapped yarn as defined in claim 1 wherein said surface wrappings of discontinuous fibers are held in position by fibers locked into place between said core ele-' ments.

6. A wrapped yarn as defined in claim 5 wherein said discontinuous fibers are about 9% to 15.5% of the total weight of the yarn.

References Cited UNITED STATES PATENTS 1,439,166 12/1922 Heany 57-160 2,053,123 9/1936 Alles 57-160XR 8 Astley 57-444 Bronson et a1. 57163 Donaldson et a] 57-160 Gibbons 57-144 Ellis 57-144 X Field 57-157 X JOHN PETRAKES, Primary Examiner. 

1. A WRAPPED YARN COMPRISING A CORE COMPOSED OF AT LEAST TWO CONTINUOUS INTEGRAL CORE ELEMENTS OF TEXTILE FIBERS AND SURFACE WRAPPINGS COMPOSED OF DISCONTINUOUS TEXTILE FIBERS, THE SURFACE FIBERS BEING TIGHTLY TWISTED ABOUT THE CORE WITH PORTIONS OF FIBERS LOCKED INTO PLACE IN THE CORE, AND THE CORE FIBERS BEING RELATIVELY STRAIGHT AND HELD TOGETHER AS A COMPACT BUNDLE BY THE SURFACE WRAPPINGS. 